Breakerless transistor ignition system



May 24, 1966 B H. SHORT 3,253,187

BREAKERLESS TRANSISTOR IGNITION SYSTEM Filed April 5, 1962 2 Sheets-Sheet 1 "LU L I. :47 .4 4'5 4? g0 4: y fla '10 A?! JV a 56 a 33 a a 62a 6%? 6 6a 7 TIME VOLTAGE INVENTOR.

H13 ATTOR/Vfy May 24, 1966 B. H. SHORT BREAKERLESS TRANSISTOR IGNITION SYSTEM Filed April 5, 1962 2 Sheets-Sheet 2 INVENTOR.

Brooks 1'2. 5220)? BY 6,?

United States Patent 3,253,187 BREAKERLESS TRANSISTOR IGNITION SYSTEM Brooks H. Short, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Apr. 5, 1962, Ser. No. 185,289 Claims. (Cl. 315-218) This invention relates to an ignition system for an internal combustion engine and more particularly to an ignition system wherein a semiconductor switch means, such as a transistor, controls the current flow through the primary winding of an ignition coil and wherein the conductivity of the semiconductor switch means is controlled by a pulse generating means driven by the engine.

In an ignition system for an internal combustion engine wherein an ignition coil supplies ignition power to the spark plugs, it is important that there be a predetermined relationship between the length of time that current is supplied to the primary of the ignition coil and the length of time that the current is interrupted to the primary winding. In some conventional ignition systems the ratio of on time to o time is in the neighborhood of 2 to 1, and in a conventional ignition system this means that the breaker points during a given cycle of operation are closed for a period of time which is twice the time that they are open. This ratio of on to off time in a conventional distributor that has breaker contacts is achieved by providing a cam which will cause the breaker contacts to be closed for approximately 31 of rotation of the breaker cam and then open for 14 in an eight cylinder engine distributor. Thus, as the breaker cam traverses one revolution or 360, the points are closed for 31", are then opened for 14, closed again for 31 and so on until a complete revolution is made.

The present invention is concerned with an ignition system wherein no breaker contacts are used and wherein a semiconductor switch means controls current fiow through the primary winding of an ignition coil and further wherein the conduction of the semiconductor switch means is controlled by a pulse generating means. In this type of system it is difficult to devise an arrangement wherein the on and ofi' times of the semiconductor switch meanshave the desired 2 to 1 ratio since voltage pulses of prior pulse generating means are very short in duration. It, accordingly, is one of the objects of this invention to provide a breakerless transistor ignition system wherein the desired ratio of on to oii' times of primary current is achieved.

A more specific object of this invention is to provide an ignition system for an internal combustion engine wherein a semiconductor switch means controls current flow through the primary winding of an ignition coil and wherein the conductivity of the semiconductor switch means is controlled by a pulse generating means having an output voltage wave form which is capable of maintaining a predetermined time ratio between the on and off times of the semiconductor switch means.

A further object of this invention is to provide an ignition system for an internal combustion engine wherein a semiconductor switch means such as a transistor controls current flow "through the primary winding of an ignition coil and wherein the conductivity of the semiconductor switch means is controlled by a pulse generating means which has an output voltage wave form comprised of a plurality of overlapping voltage pulses of the same polarity.

Still another object of this invention is to provide an ignition system for an internal combustion engine wherein a semiconductor switch means such as a transistor controls current flow through the primary winding of an ignition coil and wherein the semiconductor switch means has its conduction controlled by a voltage pulse generating means, the voltage pulse generating means including a rotatable magnetic rotor and a plurality of pickup coils circumferentially spaced around the rotor to provide an output voltage wave form which is comprised of a series of overlapping voltage pulses of the same polarity.

Still another object of this invention is to provide a breakerless ignition system wherein a semiconductor switch means such as a transistor controls current flow through the primary winding of an ignition coil and wherein a pulse generating device having a pickup coil is connected so as to control conduction of the semiconductor switch means, there being a diode connected in series with the pickup coil so that voltage pulses of only one polarity are used to control the conductivity of the semiconductor switch means.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings where in preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a schematic circuit diagram of an ignition system made in accordance with this invention.

FIGURE 2 is a top view of a voltage pulse generating means which controls the system of FIGURE 1.

FIGURE 3 is a sectional view taken along line 3-3 oi FIGURE 2.

FIGURE 4 is a curve of voltage versus time generated in one of the pickup coils shown in FIGURE 1.

FIGURE 5 illustrates the voltages generated in the pickup coils of FIGURE 1 where the rotor rotates through a predetermined angle.

Referring now to the drawings, and more particularly to FIGURE 1, the reference numeral 10 designates a source of direct current power which in this case is illusstrated as a storage battery. In a motor vehicle installation the storage battery 10 normally supplies direct current power for the ignition system during starting and the generator then supplies ignition power while the engine is running, all of which is Well known to those skilled in the art. One side of the battery 10 is grounded Whereas the opposite side is connected with the lead wire 12. A manually operable ignition switch 14 connects the lead wire 12 and the lead wire 16 when the switch is closed.

The ignition system of this invention uses an ignition coil which is generally designated by reference numeral 18 and which has a primarly winding 20 and a second ary winding 22. One side of the secondary winding 22 is grounded as is one side of the primary winding 20. The opposite side of the secondary winding 22 is connected with a rotor contact 24 of a conventional spark distributor 26. The spark distributor 26 has fixed electrodes 28 which cooperate with the rotating rotor contact 24 that is driven by the engine 30. The fixed distributor cap contacts 28 are connected respectively with lead wires 32 which in turn are connected respectively with the spark plugs 34 of the engine. In the embodiment to be described, the engine is an eight cylinder engine but it will be apparent to those skilled in the art that this invention will have equal application to engines of a ditierent number of cylinders.

The energizing circuit for the primary winding 20 of the ignition coil 18 is controlled by a PNP transistor 36 having emitter, collector and base electrodes. The collector electrode of transistor 36 is connected to one side of a resistor 40. The opposite side of resistor 40 is connected to one side of the primary winding 20.

The conductivity of transistor 36 is controlled by another PNP transistor 42 which has emitter, collector and base electrodes. The emitter electrode of transistor 42 is connected with junction 44 while the collector electrode of transistor 42 is connected with junction 46. The junction 46 is connected with the base electrode of transistor 36 via the lead wire 48 and is connected to one side of a resistor 50. The opposite side of the resistor 50 is connected to ground as is apparent from FIGURE 1.

The emitter and base electrodes of transistor 42 are connected by a plurality of pickup coils 52, 54, 56, 58, 60, 62, 64 and 66, which are respectively connected in series with the diodes 52a, 54a, 56a, 58a, 60a, 62a, 64a and 66a. The pickup coils 52 through 66 have voltage pulses induced therein by rotation of a rotor generally designated by reference numeral 68 and shown in greater detail in FIGURES 2 and 3. The rotor 68 is driven by the engine 30 and is driven in synchronism with the rotor contact 24.

Referring now more particularly to FIGURES 2 and 3, it is seen that the rotor 68 is comprised of a pair of pole pieces 70 and 72 which are formed of magnetic material and which are secured to a permanent magnet 74. The rotor 68 is driven by a shaft 76 journalled in a base or housing 78 formed of a non-magnetic material such as die cast aluminum. The permanent magnet 74 may be of any well-known type and may be, for example, of the ferrite type. This permanent magnet is axially magnetized so that the pole pieces 70 and 72 are at different magnetic polarities. It is seen that the pole piece 70 has radially extending teeth 70a, 70b, 70c, 70a, 70a, 701, 70g and 70b. The pole piece 72 likewise formed with eight radially extending teeth that are of the same shape as teeth 70a to 70g and which are exactly aligned but space-d from these teeth. The shaft 76 may be formed of a non-magnetic material such as stainless steel or the shaft may be magnetically isolated from the rotor by a non-magnetic insert.

It is seen from FIGURES 2 and 3 that the coil windings '52 through 66 are wound respectively on U-shaped members 52b, 54b, 56b, 58b, 60b, 62b, 64b and 66b. The U-shaped members 52b through 66b are formed of a magnetic material and the ends of these U-shaped members are positioned closely adjacent the ends of teeth 70a through 70h as the rotor 68 rotates. The same is true of the teeth on pole-piece 72. The U-shaped members 52b through 66b with their attached coils are supported by the base member 78 so that the circumferential spacing between the U-shaped members and their coils remains the same. It will be appreciated that the U-shaped members and their attached pickup coils could be supported on a rotatable timing plate that would be adjusted by a vacuum advance unit.

The radially projecting teeth 70a through 7071 of the pole piece 70 are spaced 45 apart for an eight cylinder engine. This spacing, of course, is the same for the teeth on the pole piece 72. The circumferential spacing between U-shaped members 52b and 54b is approximately 47. The same spacing is maintained between the other U-shaped members with the exception that the spacing between U-shaped member 66b and U-shaped member 52b is 31. With this sort of spacing, all of the radially projecting teeth of the pole pieces will have become aligned with a respective U-shaped member when the rotor has rotated 14 in the clockwise direction from its position as seen in FIGURE 2. In other words, when the rotor 68 has rotated 14, the radially extending tooth 70a will be in alignment with the U-shaped member 66b and the other teeth on the pole pieces-Will each have then I passed one of the respective U-shaped members. When the tooth 70a leaves the U-shaped member 6611 and approaches the U-shaped member 52b, none of the radially extending teeth will become aligned with any of the U- shaped members for a 31 angle of rotation. It can be seen from the foregoing that a 45 rotation of the pole piece 68 causes the teeth of the rotor to be aligned progressively with the U-shaped members for 14 of the total 45 and to be out of alignment with all the U-shaped members for 31 of the 45.

'Referring now to FIGURE 4, a curve of voltage versus time for one of the coil windings 52 through 66 is illustrated where one of the teeth approaches a U-shaped member and then passes by the U-shaped member. The point A on the curve of FIGURE 4 corresponds to the situation where one of the radially extending teeth, for example, tooth 70a, is approaching the U-shaped member 66b. From point A to point B on the curve of FIGURE 4, a voltage is induced in the coil winding 52 because of the rapid change in flux due to the tooth 70a moving into alignment with the U-shaped member 66b. At point C on FIGURE 4, the rotor teeth are exactly aligned with the U-shaped member so that there is no longer a change in flux and the voltage reduces to zero. As the radially extending teeth now leave a U-shaped member, the voltage curves goes from point C to point D in FIGURE 4 indicating that a voltage of induction has been produced which is of an opposite polarity to that produced as the radially extending teeth approached the U-shaped member. As the radially extending teeth move completely away from a given U-shaped member, the voltage decays from point D to point E. From the foregoing, it can be seen that as a pair of rotor teeth pass by a U-shaped member, a voltage curve is developed having the wave form shown in FIGURE 4.

The actual voltage that is applied between the base electrode of transistor 42 and the junction 44 or across the emitter and base electrodes of transistor 42 for a 14 rotation of rotor 68 is depicted in FIGURE 5. 'It is seen that the portion of the voltage curve between points A and C in FIGURE 4 has been eliminated, and this is due to the provision of the diodes 52a through 66a which will not permit current flow in this direction. It is seen from FIGURE 5 that the voltage curve which remains is the curve of voltage from points C to E in FIGURE 4. It is also seen that these voltage pulses overlap and develop an envelope of voltage which corresponds to a 14 rotation of the rotor 68. This overlap in voltage is due to the fact that the teeth on the rotor 68 progressively lbecome aligned with the U-shaped members 52b through 66b as the rotor 68 rotates. After the last voltage pulse has been developed or induced in the coil winding 66, the voltage will go to zero for 31 since none of the teeth on the rotor 68 will be aligned with the U-shaped members. It will be appreciated that a substantially square voltage is developed for 14 rotation of rotor 68 and then no voltage for the next 31 of rotation. Eight voltage pulses each of 14 duration are thus provided for each revolution of rotor 68.

Referring now more particularly to FIGURE 1, the ignition system of this invention may be set into operation by closing the ignition switch 14. As the engine 30 is now cranked or is running, the rotor 68 is driven as is the rotor contact 24. When no voltage is being developed between junction 44 and. the base electrode of transistor 42 from the pick-up coils 52 through 66 which correspond to the 31 interval, the transistor 42 will be substantially noncondtuctive between its emitter and collector electrodes since its emitter and base electrodes will have substantially the. same potential. With transistor 42 nonconductive in its emitter-collector circuit, the junction 46 has a potential which is substantial equal to ground potential. With junction 46 at ground potential, a base circuit can be traced for the transistor 36 which is through the resistor 50 to ground. With base current flowing in transistor 36, the transistor turns on in its emittercollector circuit and. current therefore flows through the primary winding 20 of the ignition coil. The primary winding is energized from battery 10, through the closed ignition switch 14, through junction 38, through the emitter-collector circuit of transistor 36, through resistor 40 and then through the primary winding 20 to ground. Magnetic flux is now built up in the magnetic circuit of the ignition coil 18 since there is a path for primary winding current. As the rotor 68 continues to rotate, the time will come when a voltage is developed in the coil winding 52 and an envelope of voltage will be developed as shown in FIGURE 5 for the next 14 of rotation of the rotor 68. At the beginning of this envelope of voltage and as long as it continues, the emitter electrode of transistor 42 is driven positive with respect to the base electrode. This will cause a base current to tlow in the transistor 42 with a consequent emitter to collector current. With transistor 42 turned on in its emittercollector circuit, the junction 46 will have substantially the same potential as the junction 44 and there, therefore, will be substantially no dift erence in potential between the emitter and base electrodes of transistor 36. This will turn the transistor 36 off in its emitter-collector circuit and interrupt the current flow through the primary winding 20. When this current flow is interrupted, a large voltage is induced in the secondary winding 22 which is applied to one of the spark plugs 34 through the rotor contact 24 and one of the distributor cap electrodes 28.

As the rotor 68 makes one complete revolution, there will be eight envelopes of voltage developed, each of 14 duration, separated .by eight 31 degree intervals of no voltage. This results, during one revolution of rotor 68, in transistor 36 being turned on eight times, each for 31 of rotation, and turned off eight times, each for 14 of rotation.

It can .be seen from the foregoing that a breakerless transistor ignition switch has been provided wherein the semiconductor switch means 36 is turned periodically on and ofi and wherein the on time of this transistor 36 is approximately twice the oil time for a given part of a complete rotation of the rotor 68. This results in a very eflicient internal combustion engine ignition system which has no breaker contacts to wear out and which provides high ignition power for the engine 30. It will be appreciated that the magnetic circuit for a given pickup coil winding is from one end of the magnet 74, through a pole piece, then through a U-shaped member, and then through a pole piece back to an opposite side of the permanent magnet 74.

While the embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In an ignition system for an internal combustion engine, the combination comprising, an ignition coil having a primary winding and a secondary winding, a semiconductor switch means for controlling an energizing circuit for said primary winding, and voltage pulse generating means including a rotatable part driven by said engine for controlling the conductivity of said semiconductor switch means, said voltage pulse generating means having an output voltage wave form which is comprised of a plurality of unidirectional overlapping voltage pulses of the same polarity which are continuously generated over a first predetermined angle of rotation of said rotatable part and which form a series of voltage envelopes separated by intervals of no output voltage over a second predetermined angle of rotation of said rotatable part.

2. In an ignition system for an internal combustion engine, the combination comprising, an ignition coil having a primary winding and a secondary Winding, an energizing circuit for said primary winding including a semiconductor switch means, means for baising said semiconductor switch means conductive, and means driven by said engine for biasing said semiconductor switch means nonconductive in synchronism with said engine, said last named means including voltage generating means which has an outputvoltage wave form comprised of a series of unidirectional voltage pulses defining a voltage envelope which is substantially a unidirectional square wave, said square waves being separated by time intervals of no voltage output, said square wave biasing said semiconductor switch means nonconductive, said semiconductor switch means being biased conductive during said timed interval of no voltage output.

3. In an ignition system for an internal combustion engine, the combination comprising, an ignition coil having a primary winding and a secondary winding, an energizing circuit for said primary winding including a semiconductor switch means, means for biasing said semiconductor switch means conductive, and magnetic voltage pulse generating means driven by said engine and including a rotor for controlling the conductivity of said semiconductor switch means, said voltage generating means having 'a unidirectional voltage output wave form comprised of substantially square wave voltages separated by time intervals of no voltage output, said square wave voltage pulses being generated when said rotor rotates through a predetermined angle to bias said semiconductor switch means nonconductive, said no voltage output being obtained when said rotor rotates further through a greater angle, said semiconductor switch means being conductive when said generator has said no voltage output.

4. In an ignition system for an internal combustion engine, the combination comprising, an ignition coil having a primary winding and a secondary winding, an energizing circuit for said primary winding including a semiconductor switch means, means for biasing said semiconductor switch means conductive, and magnetic voltage pulse generating means including a rotor driven by said engine for biasing said semiconductor switch means nonconductive, said voltage pulse generating means having a voltage output wave form comprised of a series of substantially unidirectional square wave voltage pulses which are operative to bias said semiconductor switch means nonconductive separated by time intervals of no voltage output where said semiconductor switch means is conductive, the time ratio of said no voltage output and said square wave pulses being substantially two to one when said rotor is driven through a predetermined angle at a constant speed.

5. In an ignition system for an internal combustion engine, the combination comprising, an ignition coil hav ing a primary winding and a secondary winding, an energizing circuit for said primary winding including a semiconductor switch means, means for biasing said semiconductor switch means conductive, magnetic voltage pulse generating means including a rotor driven by said engine for biasing said semiconductor switch means nonconductive, said voltage pulse generating means developing a substantially square wave unidirectional output voltage when said rotor is rotated through a first predetermined angle which is operative to bias said semiconductor switch means nonconductive and having no output voltage when said rotor is further rotated through a second predetermined angle where said semiconductor switch means is biased conductive, the ratio of said first and second angles being substantially one to two.

6. The system according to claim 5 wherein the semiconductor switch means is a transistor.

7. An ignition system for an internal combustion engine comprising, a source of direct current voltage, an ignition coil having a primary Winding and a secondary winding, a spark plug for said engine, means connecting said secondary winding with said spark plug, a semiconductor switch means connected with said voltage source and with said primary winding for controlling the current flow through said primary winding, means for biasing said semiconductor switch means conductive, and voltage pulse generating means driven by said engine for biasing said semiconductor switch means nonconductive, said voltage pulse generating means including a rotor driven by said engine and a plurality of circumferentially spaced pickup coils that completely encircle and magnetically cooperate with said rotor, said coils being connected in parallel and with said semiconductor switch means whereby the voltage generated in said coils is operative to bias said semiconductor switch means nonconductive, said semiconductor switch means being conductive when no voltage is generated in said coils.

t3. An ignition system for an internal combustion engine comprising, a source of direct current voltage, an ignition coil having a primary winding and a secondary winding, a first transistor having emitter, collector and base electrodes, means connecting the emitter-collector circuit of said first transistor with said voltage source and with said primary winding, a second transistor having emitter, :base and collector electrodes, means connecting the emitter-collector circuit of said second transistor across said voltage source, means connecting the base electrode of said first transistor with the collector electrode of said second transistor, voltage pulse generating means including a rotor driven by said engine and a plurality of circumferentially spaced pickup coils, a plurality of diodes, and means connecting each pick-up coil in series with a respective diode and each series connected diode and pickup coil across the emitter and base electrodes of said second transistor 9. In an ignition system for an internal combustion engine, the combination comprising, an ignition coil having a primary winding and a secondary winding, an energizing circuit for said primary winding including a semiconductor switch means, and voltage pulse generating means driven by said engine including a rotatable rotor for controlling the conductivity of said semiconductor switch means, said voltage pulse generating means having a plurality of circumferentially spaced pickup coils, all of which are spaced from one another an equal distance with the exception of two of said coils which are spaced apart a distance less than the others.

10. In an ignition system for an internal combustion engine, the combination comprising, an ignition coil having a primary winding and a secondary winding, an energizing circuit for said primary winding including a semiconductor switch means, means for biasing said semiconductor switch means conductive, and voltage pulse generating means driven by said engine for biasing said semiconductor switch means nonconductive, said voltage pulse generating means developing an output voltage over a first predetermined angle which is operative to bias said semiconductor switch means nonconductive and developing no output voltage over a second predetermined angle of rotation of said rotor, said semiconductor switch means being conductive when no output voltage is developed by said pulse generating means, said first angle being substantially 14 and said second angle being substantially 31.

11. Thesystem according to claim wherein the semiconductor switch means is a transistor.

12. An ignition system for an internal combustion engine comprising, an ignition coil having a primary winding and a secondary winding, a source of direct current, a semiconductor switching device, means for biasing said semiconductor switching device to a conductive condition where it connects said source of direct current and said primary winding, and voltage pulse generating means including rotatable means driven by said engine for generating a voltage which is operative to periodically turn oif said semiconductor switch means and to maintain said semiconductor switch means turned 011 over a predetermined angle of rotation of said rotatable means, said generated voltage having an output voltage wave form which is comprised of a plurality of partially overlapping unidirectional voltage pulses.

13. An ignition system for an internal combustion engine comprising, a source of direct current, an ignition coil having a primary winding and a secondary winding, a semiconductor switching device connected with said source of direct current and with said primary winding for controlling the energization of said primary winding,

said semiconductor switching device and said source of direct current being connected such that said source of direct current biases said semiconductor switching device to a conductive condition, and a voltage pulse generating means including a rotatable element driven by said engine for generating a voltage which is operative to turn off said semiconductor switch means and to maintain said semiconductor switch means turned 01f over a predetermined angle of rotation of said rotatable element, said voltage pulse generating means producing an output voltage Wave form which is comprised of a plurality of partially overlapping unidirectional voltage pulses that are operative to bias said semiconductor switching device nonconductive, said semiconductor switching device being biased to a conductive condition by said source of direct current when there is no output voltage from said voltage pulse generating means.

14. An ignition system for an internal combustion engine comprising, an ignition coil having a primary winding and a secondary winding, a source of direct current, a semiconductor switching device, means connecting said semiconductor switching device and said primary winding in series across said source of direct current, means for biasing said semiconductor switching device to a conductive condition, and means for periodically switching said semiconductor switching means to a nonconductive condition for a period of time which is less than the time that said semiconductor switching device is conductive, said last named means including a voltage generating means developing a time varying voltage output comprised of a series of unidirectional substantially square wave pulses which are operative to bias said semiconductor switching device nonconductive separated by intervals of no output voltage, the duration of time of said unidirectional square wave pulses being less than the duration of time of said no voltage output interval, said semiconductor switching device being biased to a conductive condition during the interval of time when said generating device has no output voltage.

15. In an ignition system for an internal combustion engine, the combination comprising, an ignition coil having a primary winding and a secondary winding, an energizing circuit for said primary winding including a semiconductor switch means, a voltage generating means having a rotatable part driven by said engine connected with said semiconductor switch means, said voltage generating means developing a time varying unidirectional voltage comprised of a series of substantially square wave unidirectional pulses over a first predetermined angle of rotation of said rotatable part, said series of unidirectional pulses being separated by intervals of no output voltage over a second predetermined angle of rotation of said rotatable part, means for biasing said semiconductor switch means conductive, said square wave pulses being operative to bias said semiconductor switch means nonconductive and to maintain said semiconductor switch means nonconductive as said rotatable part rotates through said first predetermined angle of rotation, said semicon ductor-swit-ch means being biased conductive over said second angle of rotation of said rotatable part, said second angle of rotation being larger than said first angle of rotation.

References Cited by the Examiner UNITED STATES PATENTS 2,170,892 8/1939 Cox 310152 2,300,117 10/1942 Harmon 310152 2,301,758 11/1942 Smith et a1 315222 X 2,985,797 5/ 1961 Williams et al 315-209 3,034,018 5/1962 Rosenberg 315209 3,052,818 9/1962 Sherwood et al. 315209 JOHN W. HUCKERT, Primary Examiner. JAMES D. KALLAM, ARTHUR GAUSS, Examiners. L. ZALMAN, Assistant Examiner. 

1. IN AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE, THE COMBINATION COMPRISING, AN IGNITION COIL HAVING A PRIMARY WINDING AND A SECONDARY WINDING, A SEMICONDUCTOR SWITCH MEANS FOR CONTROLLING AN ENERGIZING CIRCUIT FOR SAID PRIMARY WINDING, AND VOLTAGE PULSE GENERATING MEANS INCLUDING A ROTATABLE PART DRIVEN BY SAID ENGINE FOR CONTROLLING THE CONDUCTIVITY OF SAID CONDUCTOR SWITCH MEANS, SAID VOLTAGE PULSE GENERATING MEANS HAVING AN OUTPUT VOLTAGE WAVE FROM WHICH IS COMPRISED A PLURALITY OF UNIDIRECTIONAL OVERLAPPING VOLTAGE PULSES OF THE SAME POLARITY WHICH ARE CONTINUOUSLY GENERATED OVER A PREDETERMINED ANGLE OF ROTATION OF SAID ROTATABLE PART AND WHICH FORM A SERIES OF VOLTAGE ENVELOPES SEPARATED BY INTERVALS OF NO OUTPUT VOLTAGE OVER A SECOND PREDETERMINED ANGLE OF ROTATION OF SAID ROTATABLE PART. 